1. Field of the Invention
The present invention relates to a cooling system for an electric motor of a vehicle, the cooling system including an electric motor for driving the vehicle, and a reduction gear for adjusting a driving force of an output shaft of the electric motor to transmit the driving force to a drive shaft.
2. Description of the Related Art
In an electric motor for driving an electric vehicle, a rotor generates heat due to an eddy current loss and a hysteresis loss, which occur in an iron core thereof, and therefore, members of the electric motor are deteriorated due to temperature rise. Accordingly, a drive time of the electric motor needs to be controlled in order to suppress temperature rise.
Regarding this problem, there has been known a cooling system for cooling the rotor by flowing a refrigerant such as oil through the inside of the output shaft of the electric motor or the inside of the iron core of the rotor (refer to Japanese Patent Application Laid-Open No. H9-182375 (published in 1997)).
In the conventional cooling system, the refrigerant after being used for cooling is taken from the inside of the rotor to the inside of a motor case, and collected inside the motor case to be circulated.